Impact wrench

ABSTRACT

Fluid operated impact wrench or similar power tool apparatus wherein a tool actuator particularly a rotary impactor is moved by fluid power to move a tool by mechanical impacts of the actuator, against a force resistive to the moving of the tool. In response to the mechanical impacts of the tool actuator, a series of fluid control impulses is generated. An arrangement is provided which is controlled by the force resistive to the moving of the tool, for controlling the fluid power by said series of fluid control impulses.

United States Patent [191 1 Sept. 30, 1975 Hess I 1 IMPACT WRENCH [75]Inventor: Johann Hess, Stuttgart. Germany [7 3] Assignee: Robert Bosch(;.m.b.H., Stuttgart,

Germany 221 Filed: Feb. 26, 1974 21] Appl. No.: 446,020

[30] Foreign Application Priority Data May 23, 1973 Germany 2326171 [52]US. CL... 173/12; 173/935 lrinu1r Evuminer-James A. Leppink Attorney,Agent, or FirmMichael S. Striker 5 7 I ABSTRACT Fluid operated impactwrench or similar power tool apparatus wherein a tool actuatorparticularly a rotary impactor is moved by fluid power to move a tool bymechanical impacts of the actuator, against a force resistive to themoving of the tool. In response to the mechanical impacts of the toolactuator, a series of fluid control impulses is generated. Anarrangement is provided which is controlled by the force resistive tothe moving of the tool, for controlling the fluid power by said seriesof fluid control impulses.

13 Claims, 4 Drawing Figures [51] Int. Cl. B25B 19/00 [58] Field ofSearch 173/12, 93.5

[56] References Cited UNITED STATES PATENTS 3,515,251 6/1970 Clapp173/12 I 5 1 I 1 V//, 17,

n i H t. f F I U.S. Patent Sept. 30,1975 Sheet 2 of3 3,908,766

US. Patent Sept. 30,1975 Shet3 01-3 3,908,766

IMPACT WRENCH BACKGROUND OF THE INVENTION In known impact wrencharrangements of the indicated type, axial motions of the impactor aretransferred to a shaft provided with free wheeling means. When thisshaft has been rotated by a predetermined angular distance, it releasesa mechanical device for deactivating the fluid power drive means. Theknown, mechanical control devices for this purpose are composed of alarge number of parts, some of which are rather complicated. As aresult, the known apparatus requires much service and repair,particularly when the impact wrench is subjected to rough use. Inaddition the known complex apparatus is rather expensive.

SUMMARY OF THE INVENTION The invention overcomes the difficulties of theconventional impact wrenches by means of a fluid operated control unitfor the fluid power motor, which allows relatively simple as well asreliable control in response to the forces resistive to the moving ofthe tool.

The new control unit comprises means for generating a series of fluidcontrol impulses in response to the mechanical impacts of the toolactuator. It further comprises means controlled by theforce resistive tothe moving of the tool, for controlling the fluid power by saidgenerated series of fluid control impulses.

In particular, the control unit comprises means for generating theseries of fluid control impulses in re sponse to axial reciprocation ofthe impactor, and means controlled by tool torque resistance, forcontrolling the fluid power by the generated series of fluid controlimpulses.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTIONLOF THE DRAWING FIG. 1 of the drawing is a side view,partly in central vertical section, of a preferred embodiment of theinvention;

FIG. 2 is an end view of the apparatus, the view being taken from theright end of FIG. 1;

FIG. 3 is a partial view of the apparatus, generally similar to theright-hand portion of FIG. 1 but showing part of the apparatus insection taken along line III-III in FIG. 2; and

FIG. 4 is a view generally similar to FIG. 3 but showing a section takenalong line IVIV in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The impact wrench has agenerally drum-shaped housing 1, having a lower extension to provide theusual pistol grip 2. The housing contains an impact mechanism 3, shownat the left end of FIG. 1; a control unit 4 shown at the right end ofthe same Figure; and any suitable rotary motor for fluid power operationsuch as a compressed air vane motor, between the mechanism and the unit4, the details of this motor not being illustrated as they are known tothe art. The control unit 4 serves to inactivate the fluid power meterthe impact mechanism 3 has built up a predetermined tightening torque ofthe driven tool. According to the invention this control unit 4 usesfluid pressure impulses for this purpose.

Impact mechanism 3 is of the type having an impactor guide housing 5rigidly secured to the power output means of the vane motor, thishousing 5 being rotatably supported in the drum 1 by roller bearings 6.The impactor guide housing 5 has inner grooves 7 parallel to the axis ofthe apparatus, and keys 8 are in mesh with the grooves 7, the keys 8being provided on the outside of a hammer or impactor 9. The front ofthe hammer 9 has cogs l0 thereon, for rotary impact againstcorresponding cogs 11 on an anvil 12. This anvil 12 is shown as beingheld in the housing 1,'for rotation subject to friction. At its frontend, shown at left, the anvil 12 has a tool head 13, whereon a socketkey of the tool can be secured.

Power fluid, such as compressed air, is brought to the vane motorthrough an inlet valve with actuating trigger 24, and through areversing valve for rotating the motor either clockwise orcounterclockwise. The details of the inlet and reversing valves are notshown, being well known to persons skilled in the art.

In accordance with the invention the preferred embodiment as shown inFIG. I has a control shaft 14 rigidly coaxially secured to the anvil l2,centrally of the hammer 9. This control shaft 14, as shown, has a collar15 at an end of the shaft 14 between the hammer 9 and the vane motor,this collar 15 being rigid with the shaft 14 and having a helicalsurface 16, facing the hammer 9. A ball 17 is interposed between thesurface 16 and the hammer 9 and is held in contact with the hammer 9 bya compression spring 18, disposed in an axial recess of the hammer 9around the control shaft 14 and reacting at its left end against theanvil 12 and at its right end against a clutch ring 19 in the recess ofthe hammer 9. The collar 15 and the control shaft 14 rigid therewith areheld against rightward axial motion, but are subject to rotation aboutthe axis of the shaft 14, by an axial bearing in one end of guidehousing 5 (not shown).

The control shaft 14 has an axial bore which receives a push rod 21extending into the control unit 4. This rod 21 is secured to the clutchring 19 by a pin 23 extending through longitudinal slots 22 in thecontrol shaft 14, so that axial movements of the hammer 9 are followedby the rod 21.

The control end of this rod 21 is shown in FIG. 3, and cooperates withthe further control apparatus of FIG. 4. As shown in the latter Figure,a duct 26 is formed in the control unit 4, and it will be understoodthat compressed air passes upwardly through this duct and then forwardlyto the motor, when the inlet valve controlled by the trigger 24 (FIG. 1)is open; however, the duct 26 can be closed by a cylindrical controlslider 27, to interrupt the compressed air stream to the motor.Normally, the slider 27 is held in the position shown in FIG. 4 and theduct 26 is open, by the operation of a compression spring 28-which abutsagainst the wall of the housing at its left end and against the insideof the slider 27 at its right end. The right end of the slider alsocarries a piston 29 which slides in a suitably enlarged coaxial portionof a guide bore 30. At its outer end the guide bore 30 is closed by athreaded plug 31.

A control duct 32 (FIG. 3) for control of the fluid pressure foroperating the tool has a terminal portion 32a (FIG. 4) which leads tothe enlarged part of the guide bore 30, behind the piston 29. Ahead ofthis enlarged part, the control duct 32, 320 can be vented to theatmosphere through a vent 34, which is normally closed by a closuremember 35. This member 35 is shown as a free piston, normally forcedupwards by the pressure of the compressed air stream for operating theimpact wrench motor. When such a pressure is present in the duct 26, thepiston 35 closes the vent 34. When pressure in the duct 26 is reduced byclosure of this duct by the slider 27, while there is pressure in theend part 32a of the control duct 32, the piston 35 is forced down bythis latter pressure and the vent 34 is opened thereby.

The control valve 33 has a valve plug or plate 36 in form of a discreciprocable by the push rod 21, which rod transmits the axial motion ofthe hammer 9 to this valve plate 36. When the hammer 9 is innon-impacting position, the push rod holds the plate 36 in rightwardlyshifted position, as, shown in FIGS. 1 and 3. This construction providesa particularly simple embodiment of the invention. In said rightwardlyshifted and valve closing position of the valve plate 36, the platesep'arates a pressure inlet port 37, in the seat of the valve 33, from apressure outlet port 38 in this valve seat. The pressure inlet port orbore 37 receives compressed air from the manually actuated on-off valve,which is connected with the trigger 24, through a channel 39, while thepressure outlet bore 38 is permanently connected with the control duct32, which in turn is connected to the end part 32a across a throttlevalve 40.

Operation of the Preferred Embodiment:

The drive motor (not shown) rotates the hammer guide housing 5 andthereby rotates the hammer 9, as usual. By means of friction at the rearend of the hammer, transmitted by the ball 17 and the surface 16, thecollar and the control shaft 14 transmit a rotary force to the anvil 12.At the same time a further portion of the rotary moment of the hammer 9is transmitted to the anvil 12 by the clutch plate 19 and thecompression spring 18. Thus the anvil 12 tends to rotate with the hammer9. If this rotation of the anvil 12 is impeded by torque resistance, forexample, if a nut, rotated by the tool end 13, meets with resistance dueto threading it on a bolt, the hammer 9 and the anvil 12 will rotaterelative to each other. The ball 17 then rolls along the helical path 16and thereby axially shifts the hammer 9 into its impacting position,causing an impact between cogs 10 and 1]. Since the helical path 16 thenreaches its end, ball 17 is then released, allowing hammer 19 to bereturned rightwardly by spring 18, thereby disconnecting cogs 10, 11promptly after their mutual impact. The continuing rotation of thehammer causes repetition of this operation. Thus the impacting mechanismperforms impact actions at 10, 11 until either the torque load appliedto the anvil 12 has been overcome, or the impacting mechanism has beendeactivated.

Such deactivation of the impact mechanism is effected when a certainpredetermined torque has been reached by the tool. According to theinvention the deactivating operation is effected as follows (FIG. 3):

On each impact operation of the hammer 9, the push rod 21 briefly opensthe control valve 33, admitting a certain amount of compressed air-acontrol impulse-to the control duct 32 and, across the throttle valve40, to the terminal portion 320 of this duct. After a certain number ofsuch control impulses, pressure has been built up in the space behindthe piston 29 of the blocking slide 27, thereby shifting this slide(FIG. 4) into a position thereof wherein it blocks the compressed airstream' previously admitted to the impact wrench motor and thusarresting the motor. These operations cause reduction of pressure in theduct 26, so that the closure member 35 then opens the vent 34, allowingescape of the compressed air which still remains in the control duct.The spring 28 then shifts the blocking slide 27 back into its normalposition, thereby readying the apparatus for new operation.

It is generally preferred to construct the apparatus so that the usercan adjust the number of impacts of the impact mechanism, needed todeactivate the motor. Such adjustment can be provided by a number ofdevices, for example by means (not shown) for varying the force of thecontrol spring 28. A particularly simple as well as fine adjustment isprovided by controlling the increments of pressure in the space behindthe piston 29. For this purpose the throttle 40 has a knurled end nut 44which can be manually set, relative to a portion 43 of the throttlevalve housing, locking the parts 43, 44 relative to one another andthereby adjusting the throttle. It will be understood that for thispurpose the throttle 40 can have a needle shaped end disposedconcentrically to a seat at the inner end of a throttle housing 41, anda threaded stern of said needle, as shown.

It is further preferred to arrange the device so that it either providesthe automatic deactivating of its motor, as described, or omits thesame, as when the impact wrench is used for unscrewing a bolt. For thispurpose the throttle housing 41 (FIG. 3) can be inserted in the endpiece of the impact wrench in a plurality of positions. In theillustrated position the control impulses generated by the control valve33 are admitted to the throttle and thereby to the end part of thecontrol duct 32, 320, through a small bore 45 in the side wall of thethrottle housing 41. It will be understood that this housing can beturned so as to disconnect this small bore from the control duct 32. Ineither position the throttle housing 41 can be held, for example by aball catch 42. When the bore 45 is connected to the control duct 32,fluid admitted by the control valve 33 passes through the throttle 40,at a pressure reduced thereby, and to a throttle outlet 46. This outlet(FIG. 4) then leads the fluid, as a control impulse, to the slider unit29, 27 for the control of the impact wrench.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended:

1. In a power tool, a combination comprising a fluidactuated motor;means for supplying pressurized fluid to said motor; actuator meansdriven by said motor and generating a series of impacts; means forsensing the occurrence of each impact and for generating a pressurepulse in response thereto; and means for interrupting the supply of saidpressurized fluid to said motor when a predetermined cumulative numberof said pulses has been generated.

2. Apparatus as defined in claim 1 wherein said sensing means comprisesa control duct and a valve and valve plug in said duct for controllablyadmitting fluid pressure to the duct; and a push rod interconnecting thevalve plug with the actuator means.

3. Apparatus as defined in claim 2 wherein said valve has a seatsurface, a port aperture in said surface for admitting fluid pressurethereto, a further port aperture in said surface for transmittingpressure therefrom to the control duct, and the valve plug is adisc-shaped plate movable onto and away from said seat by said push rod.

4. Apparatus as defined in claim 1, wherein said sensing means includesa control duct, a throttle therein, and vent means connectable with saidmotor and the control duct.

5. Apparatus as defined in claim 4 wherein the throttle is disposedbetween said vent means and said sensing means.

6. Apparatus as defined in claim 4 wherein said throttle has a throttlevalve body and means are provided for selectively connecting thethrottle valve to the control duct and disconnecting it therefrom.

7. Apparatus as defined in claim 4 wherein the throttle has means foradjusting the same to thereby modify the number of pulses needed forcontrolling said fluid power motor.

8. An impact wrench comprising a fluid power motor and an impactordriven thereby for effecting rotary motion of a tool; means for axiallyreciprocating said impactor during such rotary motion to rotate the toolby impacts in response to a torque resistance; means for generating afluid control impulse in response to an axial reciprocation of saidimpactor and including a control duct and a valve and valve plug in saidduct for controllably admitting fluid pressure to the duct, and a pushrod interconnecting the valve plug with the impactor, said valve havinga seat surface, a port aperture in said surface for admitting fluidpressure thereto, a further port aperture in said surface fortransmitting pressure therefrom to the control duct, and the valve plugbeing discshaped plate movable onto and away from said seat by said pushrod; and means controlled by said torque resistance for controlling saidfluid power motor by such fluid control impulses.

9. An impact wrench comprising a fluid power motor and an impactordriven thereby for effecting rotary motion of a tool; means for axiallyreciprocating said impactor during such rotary motion to rotate the toolby impacts in response to a torque resistance; means for generating afluid control impulse in response to an axial reciprocation of saidimpactor; and means controlled by said torque resistance for controllingsaid fluid power motor by such fluid control impulses, and including aduct for admitting fluid pressure to said motor, a slider movablebetween a first position outside said duct and a second position acrosssaid duct, means operable by fluid pressure impulses derived from saidfluid pressure for moving said slider to said second position, and aspring for nonnally biassing said slider to said first position. i

10. Apparatus as defined in claim 9 wherein said slider has acylindrical portion movable longitudinally of the axis thereof and saidspring is a compression spring coaxial with said cylinder.

11. An impact wrench comprising a fluid power motor and an impactordriven thereby for effecting rotary motion of a tool; means for axiallyreciprocating said impactor during such rotary motion to rotate the toolby impacts in response to a torque resistance; means for generating afluid control impulse in response to an axial reciprocation of saidimpactor and including a control duct; vent means connectable with thefluid power motor and the control duct, and a throttle in said controlduct between said vent means and said means for generating said fluidcontrol impulses; and means controlled by said torque resistance forcontrolling said fluid power motor by such fluid control impulses.

12. An impact wrench comprising a fluid power motor and an impactordriven thereby for effecting rotary motion of a tool; means for axiallyreciprocating said impactor during such rotary motion to rotate the toolby impacts in response to a torque resistance; means for generating afluid control impulse in response to an axial reciprocation of saidimpactor and including a control duct, a throttle therein having athrottle valve body, means for selectively connecting the throttle valveto the control duct and disconnecting it therefrom, and vent meansconnectable with the fluid power motor and the control duct; and meanscontrolled by said torque resistance for controlling said fluid powermotor by such fluid control impulses.

13. An impact wrench comprising a fluid power motor and an impactordriven thereby for effecting rotary motion of a tool; means for axiallyreciprocating said impactor during such rotary motion to rotate the toolby impacts in response to a torque resistance; means for generating afluid control impulse in response to an axial reciprocation of saidimpactor and including a control duct; a throttle therein; means foradjusting said throttle to thereby modify the numer of control impulsesneeded for controlling said fluid power motor, and vent meansconnectable with the fluid power motor and the control duct; and meanscontrolled by said torque resistance for controlling said fluid powermotor by such fluid control impulses.

* i i II R

1. In a power tool, a combination comprising a fluid-actuated motor;means for supplying pressurized fluid to said motor; actuator meansdriven by said motor and generating a series of impacts; means forsensing the occurrence of each impact and for generating a pressurepulse in response thereto; and means for interrupting the supply of saidpressurized fluid to said motor when a predetermined cumulative numberof said pulses has been generated.
 2. Apparatus as defined in claim 1wherein said sensing means comprises a control duct and a valve andvalve plug in said duct for controllably admitting fluid pressure to theduct; and a push rod interconnecting the valve plug with the actuatormeans.
 3. Apparatus as defined in claim 2 wherein said valve has a seatsurface, a port aperture in said surface for admitting fluid pressurethereto, a further port aperture in said surface for transmittingpressure therefrom to the control duct, and the valve plug is adisc-shaped plate movable onto and away from said seat by said push rod.4. Apparatus as defined in claim 1, wherein said sensing means includesa control duct, a throttle therein, and vent means connectable with saidmotor and the control duct.
 5. Apparatus as defined in claim 4 whereinthe throttle is disposed between said vent means and said sensing means.6. Apparatus as defined in claim 4 wherein said throttle has a throttlevalve body and means are provided for selectively connecting thethrottle valve to the control duct and disconnecting it therefrom. 7.Apparatus as defined in claim 4 wherein the throttle has means foradjusting the same to thereby modify the number of pulses needed forcontrolling said fluid power motor.
 8. An impact wrench comprising afluid power motor and an impactor driven thereby for effecting rotarymotion of a tool; means for axially reciprocating said impactor duringsuch rotary motion to rotate the tool by impacts in response to a torqueresistance; means for generating a fluid control impulse in response toan axial reciprocation of said impactor and including a control duct anda valve and valve plug in said duct for controllably admitting fluidpressure to the duct, and a push rod interconnecting the valve plug withthe impactor, said valve having a seat surface, a port aperture in saidsurface for admitting fluid pressure thereto, a further port aperture insaid surface for transmitting pressure therefrom to the control duct,and the valve plug being discshaped plate movable onto and away fromsaid seat by said push rod; and means controlled by said torqueresistance for controlling said fluid power motor by such fluid controlimpulses.
 9. An impact wrench comprising a fluid power motor and animpactor driven thereby for effecting rotary motion of a tool; means foraxially reciprocating said impactor during such rotary motion to rotatethe tool by impacts in response to a torque resistance; means forgenerating a fluid control impulse in response to an axial reciprocationof said impactor; and means controlled by said torque resistance forcontrolling said fluid power motor by such fluid control impulses, andincluding a duct for admitting fluid pressure to said motor, a slidermovable between a first position outside said duct and a second positionacross said duct, means operable by fluid pressure impulses derived fromsaid fluid pressure for moving said slider to said second position, anda spring for normally biassing said slider to said first position. 10.Apparatus as defined in claim 9 wherein said slider has a cylindricalportion movable longitudinally of the axis thereof and said spring is acompression spring coaxial with said cylinder.
 11. An impact wrenchcomprising a fluid power motor and an impactor driven thereby foreffecting rotary motion of a tool; means for axially reciprocating saidimpactor during such rotary motion to rotate the tool by impacts inresponse to a torque resistance; means for generating a fluid controlimpulse in response to an axial reciprocation of said impactor andincluding a control duct; vent means connectable with the fluid powermotor and the control duct, and a throttle in said control duct betweensaid vent means and said means for generating said fluid controlimpulses; and means controlled by said torque resistance for controllingsaid fluid power motor by such fluid control impulses.
 12. An impactwrench comprising a fluid power motor and an impactor driven thereby foreffecting rotary motion of a tool; means for axially reciprocating saidimpactor during such rotary motion to rotate the tool by impacts inresponse to a torque resistance; means for generating a fluid controlimpulse in response to an axial reciprocation of said impactor andincluding a control duct, a throttle therein having a throttle valvebody, means for selectively connecting the throttle valve to the controlduct and disconnecting it therefrom, and vent means connectable with thefluid power motor and the control duct; and means controlled by saidtorque resistance for controlling said fluid power motor by such fluidcontrol impulses.
 13. An impact wrench comprising a fluid power motorand an impactor driven thereby for effecting rotary motion of a tool;means for axially reciprocating said impactor during such rotary motionto rotate the tool by impacts in response to a torque resistance; meansfor generating a fluid control impulse in response to an axialreciprocation of said impactor and including a control duct; a throttletherein; means for adjusting said throttle to therEby modify the numerof control impulses needed for controlling said fluid power motor, andvent means connectable with the fluid power motor and the control duct;and means controlled by said torque resistance for controlling saidfluid power motor by such fluid control impulses.